Policyholders with the collapsed life insurer Equitable Life fear that the Government will miss its June 30 deadline for all affected people to receive details of their compensation.

More than a quarter of a million payments have been made to date, but the Equitable Members Action Group (Emag) said that, with only four weeks to go, the Treasury has a lot of ground to make up. Around a million people need to be contacted with a statement explaining whether they will get compensation, how much they will receive and when they can expect it.

The Treasury has seen a massive surge in complaints this year because of the Equitable redress scheme. Chloe Smith, the economic secretary to the Treasury, said in a parliamentary written answer that the Treasury had had 382 complaints in the financial year ending in April 2012. In the previous year it received just one, she said. All but one in 2011/12 relate to the Equitable Life Payments Scheme.

A Treasury spokesman said the complaints represented less than 0.2pc of all payments made as at March 31 2012. "The Government has kept its promise, and over 230,000 payments have been made to date. It's important that policyholders get the justice they deserve," he said.

But sources close to the Treasury say they believe that it is "on track" to make the payments depsite concerns from policyholders.

Annuitants from the collapsed insurer, who rely on their policies for their pension income, older investors and the estates of the deceased are first in the queue for compensation. The Government has agreed to pay a total of £1.5bn, spread over three years, for regulatory failure.

Paul Weir, chairman of Emag, said many policyholders were deeply disappointed by the cheques they were receiving, and that many had merely received letters asking for proof of address. He added that many policyholders found it difficult to work out how their losses had been calculated from the letters that they received.

Equitable is the world's oldest life insurer, with 1.5 million policyholders who trusted it with £26bn. But in 2000 it emerged that the company had made pension promises it couldn't afford and had a staggering £1.5bn black hole in its finances.

The fight for Equitable Lifers, as the policyholders are called, is now in its second decade. Its problems stemmed from so-called guaranteed annuity rate policies that the company sold from the Fifties. These promised to pay decent rates of income, but in the Nineties they became too expensive to honour owing to falls in interest rates and inflation. This led to cuts in bonuses and by July 2000 the insurer was unable to meet its obligations and was put up for sale. It is estimated that more than 50,000 pensioners have died since the insurer collapsed, without receiving their due compensation.

The next progress report on the Equitable compensation is expected in the summer. The Government's compensation package compensates 37,000 with-profits annuitants in full for their "relative" losses. However, many other policyholders will receive far less than they believe that they lost.

Holders of with-profits annuities, who were transferred to Prudential in 2007, will have any shortfalls made up in full in the form of a top-up to their pension income. Many of the hardest-hit victims are elderly, and said to be dying at a rate of 15 a day.

There were 60,000 with-profits annuity holders in total, a third of whom did not suffer losses. Other policyholders are expected to receive about only a quarter of their estimated losses – £600 each on average.

The letters telling policyholders how much they will receive contain a calculation of how much the Government believes people have lost, using a complex formula that is available on a website, tinyurl.com/bmfgm4s. However, for everyone except the with-profits annuitants, the amount they will receive is 22.4pc of the relative loss. This is "to meet affordability constraints", the letter says.